1. Field of the Invention
The invention relates to straps with transverse contractions provided locally along varying lengths, intended for positioning said straps within a securing means such as a mooring shackle.
2. Prior Art
Straps with transverse contractions have been obtained on shuttle looms, either by means of a texture change taking place at right angles to the contractions, or by omitting warp yarns, or by exercising a tensile stress on the weft yarn in order to bring nearer transversely the warp yarns, or still by the use of special reeds. The French Pat. No. 1,395,815 may for instance be referred to, in which there is shown the embodiment of a fabric with contractions on a shuttle loom, more particularly for manufacturing neck-ties.
The straps made on shuttle looms shown irregularities in the appearance, flexibility and thickness, more particularly at right angles to the contractions. Moreover, the cost for manufacturing them is high by reason of the low output, resulting from the low working speed of this type of loom.
To obviate these disadvantages, it was necessary to manufacture woven straps with localized contractions on automatic sickle looms having a very high output rate. The manufacture of straight straps without contraction on this type of loom is known, for instance from the teachings of the French Pat. No. 1,249,049. As shown in the figures in that patent, an automatic sickle loom operates, generally speaking, by passing a weft yarn carried by a sickle back and forth across the advancing warp yarns, a selvedge being formed by a chain stitch running along an endmost of the warp yarns. The selvedge is formed by chain stitching a selvedge thread into the warp yarns, by chaining the loops defined by warp yarns, or both. A needle is disposed to move fore and aft during formation of the chain stitch, the needle remaining in a plane parallel to the endmost warp yarn. The needle does not move transversely of the warp yarns during operation.
To manufacture such a kind of product on automatic sickle looms, it has been necessary to solve important engineering problems which did not arise with a shuttle loom. For instance, it is absolutely necessary to maintain a steady spacing between the outermost blade of the reed and the needle in order to obtain the continuity of the formation of the chain at right angles to the rectilinear selvedges of normal or reduced width, and the connecting flared selvedges.
This problem does not exist in a shuttle loom, wherein the reed is merely actuated with up and down vertical reciprocating motion.